Jg. Myers et al., EVALUATION OF THE PROXIMAL FLOW-FIELD TO CIRCULAR AND NONCIRCULAR ORIFICES OF DIFFERENT ASPECT RATIOS, Journal of biomechanical engineering, 119(3), 1997, pp. 349-356
Investigations of valvular regurgitation attempt to specify flow field
characteristics and apply them to the proximal isovelocity surface ar
ea (PISA) method for quantifying regurgitant flow. Most investigators
assume a hemispherical shape to these equivelocity shells proximal to
an axisymmetric (circular) orifice. However, in vivo flow fields are v
iscous and regurgitant openings vary in shape and size. By using cente
rline profiles and isovelocity surfaces, this investigation describes
the flow field proximal to circular and elliptical orifices. Steady, p
roximal flow fields are obtained with two-and three-dimensional comput
ational fluid dynamic (CFD) simulations. These simulations are verifie
d by in vitro, laser-Doppler velocimetry (LDV) experiments. The data s
how that a unique, normalized proximal flow field results for each ori
fice shape independent of orifice flow or size. The distinct differenc
es in flow field characteristics with orifice shape may provide a mech
anism for evaluating orifice characteristics and regurgitant flows. In
stead of the hemispherical approximation technique, this study attempt
s to show the potential to define a universal flow evaluation method b
ased on the details of the flowfield according to orifice shape. Preli
minary results indicate that Magnetic Resonance (MR) and Color Doppler
(CD) may reproduce these flow details and allow such a procedure in v
ivo.